Lower capacitance is desired for copper interconnects to improve the performance of semiconductor devices. One solution involves using dielectrics with low dielectric constant (k) values in the interconnect stacks. Another solution involves reducing the thickness of any higher k material in the interconnect stack. Typically, the material with the highest k value is the barrier layer that functions as an etch stop and copper diffusion barrier. It is desirable to reduce this barrier layer thickness or replace the higher k value material with a lower k material, such as SiCN, while maintaining copper diffusion barrier properties. However, electromigration may be worse when a lower k material is used as the barrier layer. One solution is to increase the thickness of the lower k material so that electromigration is improved, however the thickness that would be needed (35 to 50 nm) would undesirably increase the overall capacitance of the dielectric stack resulting in decreased performance. Thus, a need exists for a barrier that has a low-k value and prevents electromigration failure.
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